THE MONSTER THAT CHALLENGED THE WORLD 1957 & IT! THE TERROR FROM BEYOND SPACE 1958 DOUBLE FEATURE

THE MONSTER THAT CHALLENGED THE WORLD 1957 - Prehistoric mollusk monsters from the Salton Sea enter the canal system of California's Imperial Valley and terrorize the populace.
IT! THE TERROR FROM BEYOND SPACE 1958 - The obvious inspiration for ALIEN 1979, the first manned expedition to Mars is invaded by an unknown life form, which stows away on the rescue ship.